The present invention relates to the regulation of diesel injection systems, and in particular to an electrically or electronically controlled diesel injection systems having an emergency control apparatus.
In electrically or electronically controlled or regulated Diesel injection systems, safety devices are already known which protect the engine against an overload in case of failure. An example of such a safety system is described in German Offenlegungsschrift (laid-open application) No. 19 62 570. In the safety systems described a restoring device for a quantity-determining member is disclosed. This restoring device is activated whenever a regulatory circuit itself or a line leading from one of the individual sensors has been interrupted, with the result that the setting of the quantity-determining member then corresponds to that intended for small injection quantities.
In practical operation, it has now been demonstrated that this protective adjustment in the direction of a smaller quantity is not always satisfactory, for instance, if the Diesel engine drives a tractor and a failure occurs just when the tractor has been driven in difficult terrain. In the case of the known apparatus, the vehicle would then come to a stop at a time when high power was needed, which under some circumstances could have very expensive consequences in terms of time and money.